JPH10232552A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a developing device capable of obtaining high image quality by specifying the surface roughness of a toner carrier. SOLUTION: The developing device 10 is provided with the toner carrier 12 which is arranged to approach or come into contact with an image carrier 1 carrying an electrostatic latent image and moving in a fixed direction, in a specified developing region D and circulated in a state where the surface of the toner carrier 12 carries a toner layer. Further, the developing device 10 is provided with a toner layer forming member 13 for making the toner supplied to the toner carrier 12 the toner layer having a prescribed thickness. Further, the developing device 10 is provided with an electrified 14 which is arranged to face the toner carrier 12 carrying the toner layer and electrifies it, between the toner layer forming member 13 and the developing region D. Then, the toner carrier 12 has a surface roughness Ra of 0.1<=Ra<=1.7(μm). Therefore, the toner layer having a toner layer thickness suitable for development is formed and uniformly electrified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device which is used in an electrophotographic image forming apparatus such as a copying machine or a printer, and which visualizes an electrostatic latent image formed on an image carrier by attaching toner. .

[0002]

2. Description of the Related Art Conventionally, a toner is attached to an electrostatic latent image formed on an image carrier, which is used in an electrophotographic image forming apparatus, to visualize the electrostatic latent image to form a developed image. As a developing device, a one-component developing method using a one-component developer containing only toner and a two-component developing method using a two-component developer composed of a toner and a carrier are known. These developing devices are provided with a rotatable developer carrier at a position facing the image carrier, and the developer is carried on the surface of the developer carrier and the developer carrier is rotated by the rotation of the developer carrier. The image carrier is transported to the developing areas facing each other. In the developing area, an electric field is formed by a developing bias voltage applied between the developer carrier and the image carrier, and the electric field causes the toner to transfer to an electrostatic latent image on the image carrier, thereby causing the image carrier to move. A developed image with toner is formed on the body.

In such a developing device, it is necessary to apply a predetermined amount of charge to the toner in order to surely transfer the toner to the electrostatic latent image on the image carrier in the developing area. In a two-component developing type developing device, an electric charge is given to a toner by mixing and stirring a toner and a magnetic carrier which are separated from each other on a frictional charging sequence. Control agents can liberate and contaminate the carrier surface. Therefore, when the carrier is used for a long period of time, the charging ability of the toner gradually decreases due to the influence of the charge control agent, so that there is a disadvantage that the developer needs to be replaced. In addition, a toner concentration control device and a developer stirring device for maintaining a constant mixing ratio between the toner and the carrier are required, and a magnet for supporting the magnetic carrier inside the developer carrier is required. There is a problem that the device becomes complicated.

On the other hand, a developing device of the one-component developing system is widely used because it does not have the above-mentioned disadvantages of the two-component developing system. In a one-component developing type developing device, a developer (toner) carrier is pressed against a toner layer forming member made of an elastic material called a blade,
2. Description of the Related Art A method of forming a thin toner layer on a toner carrier and applying a charge to toner by frictional charging between the toner layer and a toner layer forming blade has been widely adopted. However, in general, it is difficult to sufficiently charge the toner because the toner charging ability of the blade is low, so that a so-called reverse polarity toner charged to a polarity opposite to a desired polarity is easily generated. There is a drawback that fog often occurs. That is, in the triboelectric charging by the blade, the ratio of the toner particles in contact with the blade is low, and particularly, minute toner may pass through the toner layer forming blade without being triboelectrically charged. In order to promote the triboelectric charging, it is conceivable to increase the pressing force of the toner layer forming blade against the toner layer.However, when the pressing force is increased, the binder resin of the toner melts due to an increase in frictional heat, and the aggregated toner May clog the blade and cause a problem that white streaks are generated in the image.

In order to solve the above-mentioned problems of the frictional charging device, a developing device of a type in which a charge is directly applied to toner has been proposed. As a developing device of this type, for example, Japanese Utility Model Application Laid-Open No. 63-138560 discloses a method in which a corona discharger is provided at a position facing a toner carrier, and ions of a desired polarity are irradiated from the corona discharger onto the toner layer. A developing device of a type in which a charge is imparted to the toner by doing so is disclosed. However, when a corona discharger is used, there is a problem that dirt adheres to the corotron wire and uniform discharge cannot be obtained. In addition, a high voltage must be applied to ionize the air layer near the corotron wire.
A high voltage of V or more is required. In addition, there is a drawback that ozone is generated during discharge.

Therefore, a developing device for applying electric charge to toner without using corona discharge is disclosed in, for example, Japanese Patent Application Laid-Open No. 54-17 / 1979.
No. 030, JP-A-62-291678 and JP-A-64-62675. These developing devices will be described with reference to FIGS. FIG. 6 is a schematic configuration diagram illustrating an example of a conventional developing device.

[0007] The developing device 30 shown in FIG.
A toner carrier 32 rotating in the direction of arrow A, a stirring / supplying member 33 for stirring the toner in the developing device 30 and supplying the toner to the surface of the toner carrier 32,
A toner layer forming blade 34 that presses against the toner carrier 32 and forms the toner supplied by the stirring and supplying member 33 into a toner layer having a predetermined thickness, and contacts the toner carrier 32 or at a small interval. A cylindrical charging electrode 35 disposed therein; a bias power supply 36 for supplying a developing bias voltage to the toner carrier 32; a toner charging power supply 37 for supplying a toner charging voltage to the charging electrode 35; Housing 3 for housing each part of the element other than the power supply
8 are provided. Developing device 3 configured as above
Using 0, a charging voltage is applied to the charging electrode 35 by the toner charging power supply 37 to form a discharge electric field in the gap between the charging electrode 35 and the toner carrier 32, and ions or electrons generated by the discharge adhere to the toner. Thus, the toner is charged.

FIG. 7 is a schematic configuration diagram showing another example of a conventional developing device. The developing device 40 shown in FIG. 7 does not include a component corresponding to the charging electrode 35 in the developing device 30 shown in FIG.
The toner charging voltage from the toner charging power source 37 is applied to the toner layer forming blade 44 that is pressed against the toner layer. The toner layer forming blade 44 forms a toner layer on the toner carrier 32 and forms a discharge electric field in a gap between the toner layer forming blade 44 and the toner carrier 32 to attach ions or electrons generated by the discharge to the toner. This causes the toner to be charged.

A developing device of the type shown in FIG. 6 or FIG.
There is an advantage that a high voltage is not required as much as a corona discharger, and the generation of ozone is small because the applied voltage is low.

[0010]

However, in these types of developing devices, the electric charge is directly applied to the toner by applying a voltage as described above, so that the toner layer and the toner layer forming blade are separated from each other. Unlike a developing device in which a charge is applied to a toner by frictional charging, an electric charge required for the toner charging is excessively sent from, for example, a charging electrode. There is a problem that a difference occurs in charge distribution between the upper layer portion and the lower layer portion of the layer, and the charge amount of the toner alone becomes non-uniform. This problem will be described with reference to FIG.

FIG. 8 is a view for explaining a problem in a case where the toner layer on the developer carrying member is thick in a developing device in which a charge is directly applied to the toner by applying a voltage. As shown in FIG. 8A, when the layer of the toner 53 adhered to the developer carrier 52 by applying a voltage to the charging electrode 51 is thin, the toner density is low.
Although unnecessary charges 54 leak from the gaps between the three via the developer carrying member 52, as shown in FIG.
When the layer of the toner 53 is thick, the density of the toner 53 is high,
For this reason, there is no gap between the toners 53, and the excess electric charges 54 adhere to the respective toners 53 unevenly without leaking to the developing carrier 52. Accordingly, the charge amount of the toner 53 alone increases, and the charge amount of the toner in the upper layer portion of the toner layer,
A difference occurs in the toner charge amount in the lower part of the toner layer.
If the development is performed in such a state, uneven flight to the developer carrier 52 may occur, and the developed image may be uneven.

On the other hand, when the layer of the toner 53 adhered on the developer carrier 52 is thin, there is a problem that it is difficult to obtain a good image density. The present invention has been made in view of the above circumstances, and has as its object to provide a developing device capable of obtaining good image quality.

[0013]

According to a first aspect of the present invention, there is provided a first developing apparatus for holding an electrostatic latent image in a predetermined developing area on a movable image carrier which moves in a predetermined direction. In a developing device for visualizing an electrostatic latent image on an image carrier by attaching toner to the electrostatic latent image, the developing device is disposed so as to be close to or in contact with the image carrier in the development area, and a toner layer is formed on the surface. A toner carrier that circulates and carries the toner, a toner layer forming member that forms the toner supplied to the toner carrier into a toner layer having a predetermined thickness, and a toner layer between the toner layer forming member and the developing area. And a charger for charging the toner layer, which is disposed to face the toner carrier carrying the toner layer, wherein the toner carrier has a surface roughness of 0.1 ≦ Ra ≦ 1.7 (μm). Must have Ra And features.

The surface roughness Ra is a ten-point average roughness (JI
SB0601-1982). In the first developing device of the present invention, the toner carrier has a surface roughness Ra of 0.1 ≦ 0.1.
Since Ra ≦ 1.7 (μm) is set, a toner layer having a toner layer thickness suitable for development is formed, and the toner layer having a toner layer thickness suitable for the development is uniformly charged. Therefore, the excess charge from the charger can be leaked to the toner carrier side, so that the excess charge does not adhere to the toner unevenly and the unevenness of the developed image is reduced. Further, a good image density can be obtained without reducing the toner layer thickness.

According to a second developing apparatus of the present invention for achieving the above object, the present invention provides a developing device that carries an electrostatic latent image on a predetermined developing area and moves the image in a predetermined direction. In a developing device that visualizes an electrostatic latent image on the image carrier by attaching toner, the developing device is disposed so as to approach or contact the image carrier in the development area,
A toner carrier carrying a toner layer on its surface and circulating; a toner layer forming member for forming the toner supplied to the toner carrier into a toner layer having a predetermined thickness; the toner layer forming member and the developing area And a charger for charging the toner layer, which is disposed opposite to the toner carrier carrying the toner layer between the toner carrier and the toner layer forming member. characterized in that to form a toner layer which is toner adhesion amount TM of .1 ≦ TM ≦ 1.6 (mg / cm 2).

According to a second developing device of the present invention, the toner layer forming member forms a toner layer having the toner adhesion amount TM in the above-described range, and the toner formed in the toner adhesion amount range. The layer is a range in which the toner forming the toner layer having a thickness that is easy to develop is uniformly charged. Therefore, excessive charge does not adhere to the toner unevenly, unevenness of the developed image is reduced, and good image density can be obtained. When the toner layer forming member is arranged on the toner carrier, the toner layer forming member can be defined by a linear pressure when the toner layer forming member is a blade. It can be defined by the gap.

Here, the charging device applies an electric field between the charging electrode disposed opposite the toner carrier and a charging voltage of a predetermined polarity to the charging electrode to apply an electric field between the charging electrode and the toner carrier. And a plurality of first power supplies, which are disposed between the charging electrode and the toner carrier and regulate an ionization region of a discharge generated in the electric field between the first power supply and the charging electrode. A control electrode having an opening, and the control electrode
It is effective to provide a second power supply for applying a voltage for forming a potential intermediate between the potential of the charging electrode and the potential of the toner carrier.

A voltage equal to or higher than the discharge starting voltage is applied between the charging electrode and the control electrode, and a voltage is applied so as not to cause a discharge between the charging electrode and the toner carrier. An electric field is generated such that ions or electrons having the polarity of the above move to the toner carrier side. Then, a strong electric field is formed by the voltage applied between the charging electrode and the control electrode, and a discharge occurs between the charging electrode and the control electrode. This discharge causes an ionization phenomenon, and avalanche phenomena generates positive ions, electrons and negative ions, but the ionization region is limited between the charging electrode and the control electrode, and between the control electrode and the toner carrier. That is, ionization does not occur in a region where the toner layer exists on the toner carrier. For this reason, ionization does not occur within the range of the thickness of the toner layer, and therefore, positive ions, negative ions, and electrons are not generated. On the other hand, an electric field smaller than that at which discharge is started is formed between the control electrode and the toner carrier, and a positive ion generated between the charging electrode and the control electrode due to the electric field effect between them, or One of the negative ions and the electrons is attracted to the toner carrier and is applied to the toner layer formed on the toner carrier. Thereby, the toner can be charged to a desired polarity.

[0019]

Embodiments of the present invention will be described below. FIG. 1 is a schematic configuration diagram showing an embodiment of the developing device of the present invention. A developing device 10 shown in FIG. 1 is arranged so as to be close to or in contact with an image carrier 1 which carries an electrostatic latent image and moves in a predetermined direction in a predetermined developing region D, and has a toner layer on the surface. A toner carrier 12 that carries and circulates is provided.

The developing device 10 includes a toner carrier 12
Is provided with a toner layer forming member 13 for forming the toner supplied to the toner into a toner layer having a predetermined thickness. Further, the developing device 10 is provided with a charger 14 for charging the toner layer, which is disposed between the toner layer forming member 13 and the development area D so as to face the toner carrier 12 carrying the toner layer. . The charger 14 is provided with a charging electrode 14 a disposed opposite to the toner carrier 12, and an ionization region of a discharge generated in an electric field, which is provided at a position between the charging electrode 14 a and the toner carrier 12. A control electrode 14b having a large number of openings for regulating the distance between the control electrode 14a and the charging electrode 14a.
A toner charging power supply 14c for applying a charging voltage of a predetermined polarity to 4a to form an electric field with the toner carrier 12.
(A first power source according to the present invention) and a charging control power source 14d for applying a voltage to the control electrode 14b to form a potential intermediate between the potential of the charging electrode 14a and the potential of the toner carrier 12.
(The second power source according to the present invention).

The developing device 10 includes the developing device 10
A toner supply member 15 that stirs the toner inside and supplies the toner to the surface of the toner carrier 12, a developing bias power supply 16 that supplies a developing bias voltage to the toner carrier 12, and components of these components other than the power source, A housing 17 is provided for housing. A DC voltage of about -200 V is applied to the toner carrier 12 by the developing bias power supply 16. Note that the voltage applied from the developing bias power supply 16 to the toner carrier 12 may be a voltage obtained by superimposing a DC voltage and an AC voltage in order to ensure good developing performance. The outer peripheral surface of the toner carrier 12 is formed by cutting a round bar or pipe of aluminum or stainless steel, and then performing mechanical processing such as sand blasting, liquid honing, emery polishing, or chemical corrosion. = 0.1 to 1.7 μm, preferably those having surface roughness Ra of about 0.1 to 1.1 μm. Alternatively, a resin layer in which conductive powder is dispersed may be formed after cutting a round bar or pipe of aluminum or stainless steel. As the toner carrier 12 of the present embodiment, an aluminum pipe having a diameter of 20 mm is cut, and then the outer peripheral surface is subjected to a sandblast anodizing treatment to have a surface roughness Ra of about 0.5 μm.

The toner layer forming member 13 is formed by applying a pressing member made of silicone rubber having a volume resistance of about 10 ⁴ to 10 ¹⁰ Ω · cm including an ionic conductor to a stainless steel leaf spring having a thickness of 0.1 mm. It is installed in a doctor system via a conductive adhesive. Further, the surface is subjected to a hardening treatment in order to improve abrasion resistance at the time of forming the layer. In the toner layer forming member 13, the toner adhesion amount on the toner carrier 12 (in this case, a non-magnetic toner is used as an example) is 0.
Set the linear pressure to 15 so that it is within 1-0.8 mg / cm ^2.
１７17 mg / cm ² . The toner adhesion amount at this time was 0.4 mg / cm ² . Further, rubber having a hardness of 20 to 80 degrees can be used.
0-60 degrees is suitable.

FIG. 2 is a diagram showing the relationship between the surface roughness Ra of the toner carrier of the developing device shown in FIG. 1 and the amount of toner transported. As shown in FIG. 2, the surface roughness R of the toner carrier 12
When a = 0.1 to 1.1 μm, the toner conveyance amount is 0.1 to 0.1 μm.
0.8 mg / cm ² , and the toner transport amount is 0.4 mg / c when the surface roughness Ra of the toner carrier 12 is 0.5 μm.
m ² .

The charging electrode 14a is formed in a cylindrical shape, and is supported so as to be rotatable around an axis. The material of the charging electrode 14a is a material containing an ionic conductor or a compound of rubber and conductive fine particles, and has a volume resistivity of 10 ^5.
It is about 10 to 10 ¹⁰ Ω · cm. This volume resistivity is preferably in the range of 10 ⁷ to 10 ⁸ Ω · cm. Further, as the charging electrode 14a, a semiconductive roll in which conductive powder is mixed in silicone rubber may be used.

The control electrode 14b is made of a stainless mesh member having a wire diameter of 50 μm and a pitch of 127 μm, and is formed in a cylindrical shape having a larger diameter than the charging electrode 14a. The control electrode 14b is extrapolated to the charging electrode 14a,
4a and the toner carrier 12, a part of the inner peripheral surface of the control electrode 14b is in contact with the charging electrode 14a at the position facing the toner carrier 12, and is driven to rotate. Further, the control electrode 14b may be laminated on the charging electrode 14a via an insulating layer. With such a configuration, the leakage of the charge from the charging electrode 14a to the toner carrier 12 may be adjusted.

In order to charge the toner on the toner carrier 12 to a negative polarity, the charging electrode 14a and the control electrode 14b
An electric field is formed so as to start a discharge between the toner carrier 1 and the electric field having such a small gradient that no discharge occurs between the control electrode 14 b and the toner carrier 12.
An electric field is generated in a direction to attract to the two sides. Therefore, the relationship between the potential of the control electrode 14b and the potential of the toner carrier 12 is maintained, for example, in the following relationship.

(Electric potential of toner carrier 12)-(Electric potential of control electrode 14b) = 100 V The relationship between the potentials of the charging electrode 14a and the control electrode 14b is maintained as follows. (Potential of control electrode 14b)-(potential of charging electrode 14a)
= 1000 V The potentials of these electrodes are appropriately determined by the distance between the charging electrode 14a and the toner carrier 12, the structure and thickness of the control electrode 14b, and the like. In addition, the charging electrode 14
When a, the control electrode 14b, and the toner carrier 12 are provided with a gap therebetween, the size is determined in consideration of the size of the gap. In the present embodiment, a voltage of −200 V is applied from the developing bias power supply 16 to the toner carrier 12, and the charging control power supply 14 is applied to the control electrode 14 b.
A voltage of -300 V from d is applied, and the shaft of the charging electrode 14a is supplied with a power of
Is applied.

The developer used in the developing device 10 of the present embodiment is a one-component type toner, and various kinds of thermoplastic resins such as styrene resin, acrylic resin or polyester resin are mixed with pigment or metal-containing azo dye. The polarity controlling agent is dispersed, pulverized and classified to 3 to 20 μm (average particle size 7 μm).
m) are used. Further, a charge control agent is added to impart a negative charge. As the charge control agent, fine particles of 0.1 μm or less such as silica, alumina, and titanium subjected to hydrophobic treatment can be used, and hydrophobic silica is most preferable. Further, a fluidity aid of the toner is externally added to stabilize the developing performance.

As the image carrier 1, a selenium-based photoconductor or an organic photoconductor is used, and the image carrier 1 and the toner carrier 1 are used.
2 may be placed in contact with
It may be arranged facing the toner carrier 12 with a gap of about m to 400 μm. In the developing device 10 configured as described above, the toner in the developing device 10 is agitated by the rotation of the toner supply member 15 and supplied to the surface of the toner carrier 12. The toner supplied to the surface of the toner carrier 12 is charged by the rotation of the toner carrier 12 to the charging electrode 14.
a to the position facing the control electrode 14 b and the toner carrier 12 by the pressing force of the toner layer forming blade 13.
A toner layer is formed thereon. The formed toner layer is transported to a position facing the charging electrode 14a and the control electrode 14b. At this time, the above-described voltage is applied between the charging electrode 14a and the control electrode 14b and between the control electrode 14b and the toner carrier 12, and an electric field is formed in a region where these oppose each other. . In such an electric field, only the side of the charging electrode 14a larger than the discharge starting electric field can discharge, and the electric field of the charging electrode 14a on the side of the toner carrier 12 does not ionize because it is smaller than the discharge starting electric field. .

FIG. 3 is a view showing the mechanism of ionization region separation in the developing device shown in FIG. As shown in FIG. 3, positive ions 22 in addition to negative ions and electrons 21 are generated in the vicinity of the charging electrode 14a due to ionization accompanying discharge, but no ionization occurs in the vicinity of the toner carrier 12, and the control electrode 14b The negative ions and the electrons 21 are attracted to the toner carrier 12 by an electric field effect between the toner carrier 12 and the toner carrier 12. The attracted negative ions and electrons 21 adhere to the toner 23 on the toner carrier 12, and the toner 23 is charged. Therefore, the positive ions 22 generated due to ionization are present only on the side of the charging electrode 14 a and are adsorbed to the charging electrode 14 a, but do not adhere to the toner 23 on the toner carrier 12. Therefore, generation of the opposite polarity toner is suppressed. At this time, since the thickness of the toner layer on the toner carrier 12 is within a predetermined range, excessive charge from the charging electrode 14a does not leak to the toner carrier 12 and overcharge in the toner layer. A uniform charge distribution is maintained.

FIG. 4 is a diagram showing the mechanism of ionization region separation in the case where no control electrode is provided between the charging electrode and the toner carrier. As shown in FIG.
Assuming that the control electrode 14b is not provided between the toner carrier 4a and the toner carrier 12, when a discharge occurs between the charging electrode 14a and the toner carrier 12, an ionization phenomenon occurs in a minute gap therebetween. I do. Then, negative ions and electrons 21 and positive ions 22 having different polarities are generated due to the effect of the electron avalanche. Electron avalanche due to this ionization phenomenon occurs in any part of the minute gap, so that ionization also occurs in the air layer inside the toner 23 layer on the toner carrier 12, and as a result, the charged toner has the desired polarity. In addition to the charged toner 23, a toner 23 of the opposite polarity, which is charged to the opposite polarity, is generated. In the developing device 10 of the present embodiment, since the control electrode 14b is provided between the charging electrode 14a and the toner carrier 12, generation of such toner of the opposite polarity can be reduced, and the toner Electrostatic aggregation can be prevented. Further, it is possible to prevent the toner carrier 12 and the toner layer from strongly adhering electrostatically, and it is possible to prevent an increase in the amount of transported toner.

The toner layer to which a uniform charge has been applied as described above is conveyed to the developing area D facing the image carrier 1 by the rotation of the toner carrier 12. Then, the toner is transferred to a latent image on the image carrier 1 by a developing electric field formed between the toner carrier 12 and the image carrier 1 and development is performed. FIG. 5 is a diagram showing a relationship between a toner conveyance amount and a toner charge distribution in the developing device shown in FIG.

When the potential of the toner on the toner carrier 12 was measured, the toner conveyance amount was 0.2, 0.8, 1.2.
(Mg / cm ² ), charging was confirmed to be from 7 μC / g to 20 μC / g suitable for development (note that the circles, squares, and triangles shown in the figure each have a large charge amount). Toner, toner having an average charge amount, and toner having a small charge amount). At this time, the toner of the opposite polarity is 0.1 wt.
% Or less, the polarity of the toner was uniform, good chargeability was obtained, and the charge distribution was sharp.

In this developing device, a scorotron can be used as a charge providing mechanism in place of the charging electrode 14a and the control electrode 14b, but it is not environmentally preferable because a large amount of ozone is generated. still,
In the developing device of the present embodiment, in addition to the effects described above, it is possible to prevent an excessive discharge current from flowing to the toner carrier 12 due to local discharge or the like, and to the extent that the toner cannot contribute to development. Until then, the charge amount does not increase. For this reason, problems such as an increase in the amount of transported toner can be avoided.

Further, in the developing device 10 of the present embodiment, a blade pressed against the toner carrier 12 is used as the toner layer forming member 13, but a roller-shaped member, a trimmer, or the like can also be used. .

[0036]

EXAMPLE A result of a long-term print test performed under the following conditions to confirm the toner charging performance of the developing device 10 of this embodiment will be described. Image carrier: negatively charged organic photoreceptor Process speed: 200 mm / sec Control electrode: A cylindrical film made of a conductive material having a thickness of 100 μm and having a fine aperture of φ80 μm at an aperture ratio of 80% Charged electrode: φ10 mm Roll-shaped member Material forming the peripheral surface: silicone rubber mixed with ionic conductor Rubber hardness: 60 degrees Volume resistivity: 10 ⁸ Ω · cm Toner carrier: Φ20 mm Surface roughness Ra: 0.1-1. 1 Amount of toner attached: 0.3 to 0.5 (mg / cm ² ) Roll having surface rubber layer (10 ⁶ Ω · cm) Toner supply member: Φ10 mm Roll made of semiconductive sponge material Toner layer forming member: SUS303 , A 1-mm-thick leaf spring bonded to a 1-mm-thick silicone rubber containing an ionic conductor with a conductive adhesive. ~120gf / cm volume resistivity: ^{10 4} ~10 10 Ω · cm rubber hardness: 60 degrees, those surfaces were hardened latent image potential: -100 V background portion potential: was subjected to printing test in -350V above conditions Thus, a uniform charge amount of the toner can be realized, and the occurrence of toner ghost, ground fogging, and toner scattering into the apparatus due to the opposite polarity toner, which were problems in the related art, could be extremely reduced.

[0037]

As described above, according to the developing device of the present invention, the amount of toner adhered to the toner carrier is set in a range where excess charge from the charger is leaked to the toner carrier. Thus, the toner layer is developed while the charge distribution in the upper layer portion and the lower layer portion is not uniform and is uniform. Therefore, unevenness in image quality is reduced.

Further, a voltage higher than a discharge starting voltage is applied between the charging electrode and the control electrode constituting the charger to generate a discharge, and an ion of a desired polarity is applied between the control electrode and the toner carrier. Alternatively, if an electric field is generated such that electrons move toward the toner carrier to prevent discharge, generation of toner of the opposite polarity during charging of the toner is reduced, and the toner can be charged substantially uniformly. Accordingly, it is possible to prevent the toners from being electrostatically aggregated, and to prevent the toners from strongly adhering to the toner carrier.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an embodiment of a developing device of the present invention.

FIG. 2 is a diagram showing a relationship between a surface roughness Ra of a toner carrier of the developing device shown in FIG. 1 and a toner conveyance amount.

FIG. 3 is a diagram showing a mechanism of ionization region separation in the developing device shown in FIG.

FIG. 4 is a diagram illustrating a mechanism of ionization region separation when a control electrode is not provided between a charging electrode and a toner carrier.

FIG. 5 is a diagram illustrating a relationship between a toner conveyance amount and a toner charge distribution in the developing device illustrated in FIG. 1;

FIG. 6 is a schematic configuration diagram illustrating an example of a conventional developing device.

FIG. 7 is a schematic configuration diagram showing another example of a conventional developing device.

FIG. 8 is a diagram for explaining a problem in a case where a toner layer on a developer carrying member is thick in a developing device that applies a charge directly to toner by applying a voltage.

[Explanation of symbols]

 Reference Signs List 1 image carrier 10 developing device 12 toner carrier 12 13 toner layer forming member 14 charger 14a charging electrode 14b control electrode 14c power supply for toner charging 14d power supply for charging control 15 toner supply member 16 developing bias power supply 17 housing 21 electron 22 plus Ion 23 toner

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jun Abe 430 Nakai-cho, Sakaigami-gun, Kanagawa Prefecture Green Tech Nakai Inside Fuji Xerox Co., Ltd. Inside

Claims (3)

[Claims] 1. An electrostatic latent image on an image carrier, which carries the electrostatic latent image and moves in a predetermined direction in a predetermined developing area, by attaching toner to the electrostatic latent image on the image carrier. In a developing device for visualizing a latent image, a toner carrier that is arranged so as to be close to or in contact with the image carrier in the development area, carries a toner layer on the surface and circulates, and is supplied to the toner carrier. Forming a toner layer having a predetermined thickness into the toner layer, and a toner layer disposed between the toner layer forming member and the developing area, facing the toner carrier carrying the toner layer. And a charger for charging the toner carrier, wherein the toner carrier has a surface roughness Ra of 0.1 ≦ Ra ≦ 1.7 (μm). 2. An electrostatic latent image on an image carrier, which carries an electrostatic latent image and moves in a predetermined direction in a predetermined developing area, by attaching toner to the electrostatic latent image on the image carrier. In a developing device for visualizing a latent image, a toner carrier that is arranged so as to be close to or in contact with the image carrier in the development area, carries a toner layer on the surface and circulates, and is supplied to the toner carrier. Forming a toner layer having a predetermined thickness into the toner layer, and a toner layer disposed between the toner layer forming member and the developing area, facing the toner carrier carrying the toner layer. The toner layer forming member has a toner adhesion amount TM of 0.1 ≦ TM ≦ 1.6 (mg / cm ² ) per unit area on the surface of the toner carrier. What forms Developing apparatus is characterized in that. 3. The charging device according to claim 1, wherein the charging device applies a charging voltage having a predetermined polarity to the charging electrode disposed opposite to the toner carrier to generate an electric field between the charging electrode and the toner carrier. A first power supply to be formed, and a plurality of openings disposed at positions sandwiched between the charging electrode and the toner carrier to regulate an ionization region of a discharge generated in the electric field between the charging electrode and the opening. And a second power supply for applying to the control electrode a voltage that forms an intermediate potential between the potential of the charging electrode and the potential of the toner carrier. The developing device according to claim 1 or 2, wherein